^ ..... that's a very generic true fact but that's not what I was getting at.

My point was in the physical design constraints of a divided housing in that the wall thickness needed to divide the housing and such limits the size it can be effectively applied to usage with. Much like turbos generally become less efficient as they decrease in size due to factors like blow-by and such. Least, that's what I've seen in terms of results.

 

For that power I would love gtx35 comp wheel matched up to me gt30 turbine wheel . I would go with the new gt3076 thats been offerd above mate



Has anyone just got a gtx35 comp wheel and got the gt3076 machined out to fit or can you just buy the housing and mate it to the 30 side ?.

 

I'm just going to vent a little bit. Nothing I say here is meant for anyone in particular, just my thoughts.

This whole "twinscroll" craze has been slightly overblown. It became the new techno buzzword to use by people that have no idea what they were talking about. There is nothing magical or "more advanced" about a "twinscroll" turbo over a regular turbo...the only difference is the exhaust is divided (there is only one "scroll" in a turbo!). The fact of the matter is the divided housing became popular because of increased efficiency at the lower end of the RPM range, where you need it for large turbos in race applications. OR, you can be like the OEM's (VW, BMW) that are using them on T28 sized turbo's for the quickest spool possible. But, like anything, there is a tradeoff which is choking off your flow at the top end. So, now the trend is to to compensate for this deficiency by putting ungodly large hot sides on T3 frame turbos, which in my mind totally defeats the purpose. When you start talking about large T4 frame turbo's on small displacement motors like ours, then I think it makes a little more sense.

To Redline - If you want a great street setup with a fast (relatively) spool, stay with a smaller turbo like a GT30 and don't worry about chasing a divided housing setup. 400whp on a 2.0-2.2L motor is going to need some RPM's, no matter what turbo you go with. That size turbo can do it in a very fun, smooth way which I think will fit your goals.

 

Spectacle- Do you think I should run a non divided turbo with my mani? Thanks for all the information so far everyone, keep it come.

 

Yes. For your power goal, its not worth the extra effort or expense.

 

Well said! This is why I've been saying I wouldn't suggest it for small or mid-frame turbos.

OP, if you run a GT3076 dont even bother with a twinscroll setup. That turbo will already provide nearly instant spool.

If you go with a large GT35 setup then perhaps start CONSIDERING a divided setup but that'd be the minimum IMO.

 

Non-divided.

Spectacle is exactly correct.

 

Then you have the thought backwards. A divided T4 inlet uses the same outer diameter as the undivided inlet, but a divider wall is added in the middle (obviously). This means the area of the inlet (in square inches or mm) is smaller for the divided housings than the undivided housings, albeit only by a marginal amount. This would mean the mass flow potential of the divided housing is more limited than the undivided, making it a better choice in smaller applications.

Im guessing you blow out, rather than blow by? Blow by is air moving past cylinder rings after the ignition stage; cylinder blow out is when a long duration cam is used in a turbo or supercharged application, and too much of the compressed air leaves the cylinder at the intake stage.

When read as a percentage, smaller turbos are almost not different in overall efficiency compared to larger ones. Its all a matter of the setup. If you are trying to make 400whp with a GT2860R, you will incur much more heat because you are pushing the compressor near the far limits of its efficiency. A GT3076R will be a much better choice, and intake temps will be lower. Its all a matter of sizing everything correctly. You can have the right turbo for your power goal but if the motor is not put together properly (like using an NA cam with forced induction) you will not have the most efficient overall setup.

Of course, its not a more advanced setup (with the exception of the valve actuated twin scroll systems) but there is a real purpose. It works off the same scientific principle as long tube 4-1 and 4-2-1 headers. Exhaust pulses are separated for longer periods of time to maintain that pulse energy and get the most benefit from it. Long tube headers use the pulse energy to effective help clear a cylinder (scavenging). 4-2-1 headers separate the pulses for longer than 4-1, and thats why they make more torque and horsepower. Turbos use it to get the most energy to the turbine wheel, giving better response and spool. If the housing is properly designed it will have very good efficiency overall, but its not uncommon for a housing to be poor in design or too small for the application.

One example of a turbo application that shows major gains from a fully divided setup is the rotary. They have very strong exhaust pulses that when used on an undivided housing will lose BOTH horsepower and torque, as well as overall response. When the pulses are "dumped" into the open housing they dissipate and lose effectiveness. The divided housings keep the energy contained and best turbo performance will be achieved.

 

I don't have it backwards, I have seen divided scrolls against the undivided counter parts head to head. I'm aware of the division and what is given up to make the divide possible. It's why I said generally you up size for a divided in my earlier post. Have you ran a divided on a S2K in a mid-frame turbo or smaller? Just curious.....
There's blow by in turbos too. Slow down a little and think about the turbo inlet, consider that the impeller wheel doesn't touch the housing, also the center section is efficient in comparison to the outer portion due to engineering constraints in the metal. If you measure the total area of the intake portion you'll find that the % of effective turbine vs total area changes with the overall size of the turbo. Technology continues to improve these factors but it's still a factor. Also the gains on this small divided setup aren't worth the trouble. I guess not everyone can be shown the light. Do less blowing out and more thorough thinking.

This is why many twin turbo setups have given way to single turbo setups. Single turbo "lag" has become more of a moot point thus a single brings greater gains for some of the reasons I explained above aside from some other more obvious reasons. This is all considered even with the gains had by twin turbos which are some of the exact same advantages a twin scroll brings to the table (separating exhaust pulses).

Numerous books by turbo engineers have taught me that smaller turbos are inefficient by nature due to engineering restrictions. I guess you know a lot more than them though on that topic.

I can see you've made your mind up.

Enjoy!

 

<T4 turbo with a fatass divided hotside.. only way to do it